2004 Volvo intermittent random misfire
I have a doozy: 2006 S40 w/s7 engine. Came to me after engine installed elsewhere with check engine light. lots of faults. the ones that returned were 2600 fuel pressure sensor and 3502 random misfire. New fuel sensor took care of 2600, but I can not resolve the random misfire. It occurs around 3k rpm, usually as engine rpm is dropping. Does not ever occur on hard accel. misfire counter shows usually on cyl 3 and 4, but never sets a specific cylinder misfire code. Never feel the misfire,never sets any other codes. Does not do it on every trip, sometimes only once a day. steps we have so far taken:
Swapped out coils and plugs.
Verified all the grounds are clean/tight and resistance is low.
Verified timing belt is on right and tensioner is not sagging.
Swapped out injectors.
Crankcase at .8 inches of vacuum.
Tested compression and leak down.
Tested for crankshaft end play.
Inspected the ring gear.
Verified that the donor car was an automatic and an S7 engine.
Scoped cams and crank sensors. patterns are clean and I can not catch any timing change issues between (so far).
Monitored every chunk of data till the cows come home.
Pedal values are accurate, throttle valve values appear accurate.
fuel pressures are steady.
All 3 o2 sensors have good freq/amplitude.
Fault occurs if cam shaft adjuster unplugged.
Swapped out ams and map sensor just for grins.
Fuel trims has higher swings than I would like, but always comes back to close to zero
Do see the live data for camshaft adjusting angle bounce around at time by 4-5 degrees, but passes camshaft adjustment test every time.
Any insights will be greatly appreciated... (edited)
I'm not very hip with Volvo, but does this need a crank relearn or whatever Volvo may call it? Do you feel misfires? If not maybe it is flagging incorrectly. If there is a relearn required, you will be chasing your tail
thanks for the reply, no learning or re-adaptation is needed. One time out of many, many many road tests I felt it miss a tiny bit….
Check you running compression and check the upperstream o2 sensor. Sometime they droop to 0 reading in one million of the second
Thanks for replying Justin. I have watched the crank and cam signals pretty extensively and never seen a deviation, at least so far. Hopefully Im not just missing it if its occuring. It unfortunately is a tough one to reproduce due to the very intermittent nature
Thanks Luis. Intake manifold is right on top of the cam cover and there isnt enough room to sneak tester in there with it on, so running tests arent viable
is the injectors the correct ones for this engine ?? had the same problem with a Subaru we swap engine and the injectors was change mid year so we had to reuse the injectors from old engine, it will work ok until you drive car and then will misfire.
thats a good question. I double checked an injectors are the same for both years/engines